Function get the top-level parent of page in WordPress

get_top_parent_id.php

<?php
/**
 * Function to get the top-level parent of a page.
 *
 * @param int $post_id The ID of the page.
 * @return int The ID of the top-level parent page.
 */
function get_top_level_parent($post_id) {
    $parent_id = wp_get_post_parent_id($post_id);
    if ($parent_id == 0) {
        return $post_id;
    } else {
        return get_top_level_parent($parent_id);
    }
}